<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <script>
    var str = ''
    for(var i = 1; i < 10; i++) {  // 行
     
      for(var j = 1; j <= i; j++) {
        // i * j = 10
        // 1 * 1 = 1  
        // 1 * 2 = 2  2 * 2 = 4
        str += i + '*' + j + '=' + i * j + '\t'
      }

      str += '\n'
    }

    console.log(str)
  </script>
</body>
</html>